In telecommunications transmission systems, there is a need for housing electronic equipment at locations between telephone central offices. The aforesaid electronic equipment may be located in manholes below ground level or in cabinets above ground level. To protect the electronic equipment from rain, dust, and physical abuse, the cabinets, when used, must be substantially closed.
Heat generated from the electronic equipment is transferred primarily by convection air current within the closed cabinet to the metallic walls thereof and then by radiation and convection to the atmosphere. For effective heat transfer by convection, large spaces must be provided for air flow between circuit boards and between the inside cabinet surfaces and the equipment on the aforesaid circuit boards.
Solar energy, incident on the cabinet walls, is conducted therethrough, raising the temperature within the cabinet.
In order to prevent failure of the aforesaid electronic components, it is necessary to maintain the temperature within the cabinet below a certain level. This objective may be achieved using known methods by air conditioning, increasing the size of the cabinet, reducing the density of the electronic equipment mounted on circuit boards, or a combination thereof. Such methods, however, increase the cost of telecommunications services.
It is desirable to use compact cabinets housing circuit boards densely packed with electronic equipment and yet maintain the temperature within the cabinet below an acceptable level.